Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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KNEE STABILIZER
~ACKGROUND OF THE INVENTION
This inven-tion relates to orthotics, to supports or
stabilizers for joints and, in particular, to a knee brace which
serves both preventive and remedial functions in protecting
against medial-lateral, anterior-posterior and rotary instabili-
ties.
The knee joint is perhaps the most susceptible to injury
of the major articulated joints of the human body, despite the
presence of five major ligaments and two menisci which serve to
connect and stabilize the tibia and femur. These anatomical
structures include the anterior and posterior cruciate ligaments,
the medial and lateral collateral ligaments, the posterior capsule
ligament and the medial and lateral menisci.
Anatomically, the knee is designed so that specific
muscles or muscle groups, not ligaments, absorb the brunt of
external or internal forces. That is, a muscle or group of
muscles substitutes for each ligament in the knee to absorb force
and restrict motion. As examples, -the hamstrings substitute for
the anterior cruciate ligament, the quadriceps for the posterior
cruciate ligament, and the abductor and adductor groups for the
medial and latera] collateral ligaments.
The articulation of the knee joint, and the ligaments,
muscles and bones associated with the joint are described, for
example, in Gray's Anatomy and in The Johns Hopkins Atlas of Human
Functional Anatomy, 2d ed., 1980.
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When a muscle i5 unable to compLetely absorb an applied
force, either because of inherent weakness or prior injury or
simply because the force is too strong, the unabsorbed component
of force is transmitted to one or more liyaments. If the trans-
mitted component is sufficiently great, the ligament is strained
or torn. Ligamental susceptibility to injury is also dependent
upon the degree of flexion or extension. However, the inherent
cooperation and relationship among the ligaments is such that when
the knee is bent or flexed, some ligaments are relatively tight
and tend to control displacement, but others are relatively loose.
Between 20-60 of flexion, the knee is very susceptihle to dis-
placement and to ;njury. This i5 unfortunate, because the knee is
frequently in this position, particularly during the more active
sports activities.
It is factors such as these which make the knee rela-
tively weak compared to the other major articulated joints. Some,
such as the ball and socket hip joint, are very secure. Others,
such as the elbow and shoulder joints are complicated but nonethe-
less relatively secure. Despite its inherent weaknesses, the knee
~0 joint must both support the weight of the body and provide for
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movemen~, while holdin~ the tibia and femur in posi-lion alony
their substantially planar unstab:Le inte~face.
In considering external forces applied to the knee and the
resulting ligamen~ injuries, it is helpful to simplify the
situation somewhat and consider ~he forces as having their major
components applied primarily along a frontal plane through the
knee, or along a sagittal plane through the knee, or as comprising
a rot~atory force. Frontal plane forces are medial-lateral forces
which displace the femur and/or tibia in a side-to-side direction.
Saggital plane forces are anterior-posterior forces ~hich displace
the femur and tibia in approximately a front-to-back motion, and
includes drawing forces applied during flexion or extension.
Rotatory forces are those which tend to induce relative rotational
displacement of or between the femur and tibia, primarily against
the stabilizing force provided by the anterior cruciate ligament.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 schematically illustrates the application of medial force
and lateral force to the human leg.
FIGURES 2A and 2B schematically illustrate respe~tively
application of an anterior tibial force and an external rotation
anterior tibial force to the human leg;
FIGURE 3 illustrates the resultant displacement of the tibia
relative to the femur.
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FIGURE 4 schematically illustrates ~he appllcation of a po.sterior
tibial force to the human leg.
FIGURES 5 and 6 are, respectively, front and side schematlc
illustrations of two conventional knee braces.
FIGURES 7, 8 and 9 are, respectively, side, front and rear
elevation views of the knee stabilizer of the present invent:ion,
including, in FIGURE 7, illustration of the positioniny of the
knee stabilizer on the human ley.
FIGURES 10, 11 and 12 are, respec~ively, side, front and rear
elevation views, in the manner of FIGUR~S 7, 8, 9, illustratiny a
light-weight, four-point pressure version of my knee stabilizer.
FIGURES 1 through 3 illustrate examples of the above forces. In
these schematic drawings, the femur, tibia and knee are
respectively designated 11, 12 and 13. Referring specifically to
FIGURE 1, two of the more common knee alignment injuries result
from medial and lateral forces. The medial collateral ligament
and lateral collateral ligament are primary stabilizing influences
against medial and lateral force, réspectively. As a conse~uence,
strains or tears of these liyaments tend to result, respectively,
from medial forces, that is, inward or medially-directed ~orces 14
applied against the outside of the leg, or lateral forces 15,
which are outward directed forces applied against the insicle of
the leg.
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Perhaps the most frequent injury in sports, and certain-
ly one of the most damaging injuries to the joints involves
strains or -tears of the anterior cruciate ligament. Referring to
the side views shown in FIG. 2, the responsible force may involve
an anterior tibial force alone, that is, a forward-directed -force
21 applied to the back of -the tibia. See FIG. 2A. The force may
involve the combination of a rotational tibial ~orce 22 which
rotates the tibia relative to the femur (as by catching a shoe or
cleats in turf) and an anterior tibial force 21. See FIG. 2B. In
either case, injury to the anterior cruciate ligament results from
excessive force which the substitutional muscles and the anterior
cruciate ligament are unable to absorb and a resulting anterior
tibial acceleration and displacement relative to the femur. See
FIG. 3. The reason for the frequent occurrence o-f this injury is
twofold, namely the frequency with which the knee and leg are
subjected to large magnitude forces, and the susceptibility to
injury in that typically the knee can withstand only about 380
pounds of force and 12.5 millimeters displacement or movement
between the tibia and the femur without injury to the anterior
cruciate ligament.
Referring to FIG. 4 and as shown by the arrow 41 there-
in, a posterior-directed force 41 is the opposite of anterior-
directed force 21. The knee 13 is stabilized against posterior
forces primarily by the posterior cruciate ligament. Unlike the
anterior cruciate ligament, the posterior cruciate ligament is
backed by the posterior capsule ligament, which is quite effective
in stabilizing the knee against displacement. As a result,
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isolated posterior cruciate tears are rare. Usually injuries to
other ligamen-ts are also involve~. In fact, it is not infrequent
that the bone at~achment itselE tears rather than, or in addition
to the posterior capsule ligament.
Displacement of the femur and tibia resultiny from rota-
tional forces such as 22, FIG. 2B, is another primary cause of
injury to the anterior cruciate ligament. Of course, if there is
existing damage or if the anterior cruciate ligament has inherent
instability, the knee is more susceptible to displacement and the
ligament is more susceptible to injury. The same is true of the
other ligaments in that existing damage or instability increases
their susceptibility to injury.
Concentrated efforts by the orthotics profession to
develop knee stabilizers are thought to have been initiated in the
1960's as a result of publicized knee injuries suffered by profes-
sional athletes. It is believed basically two types of knee
braces have dominated this field. Referring to the FIG. 5 front
view, one such brace 50 uses a three-point suspension which is
provided by two pads 51 and 52 situated above and below the knee
(on either the medial or the lateral side of the leg) and a third
pad 53 on the opposite side of the leg adjacent the knee. Rigid
braces 54-54 correct the pads. Various straps can be used to
enhance suspension and/or stabilization characteris-tics. Refer-
ring to the side view shown in FIG. 6, the second type 60 oE
conventional knee brace uses relatively rigid anterior femur and
tibial shells 61 and 62 which are joined by hinged uprights 63-63
and supported in the back or posterior side by elastic straps 64
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and 65. These designs are more effective at protectiny ayainst
medial-lateral forces than anterior-posterior ~orces. The reason
is simple. The rigid shells/pads and connecting braces provide
relatively inflexible pressure points wh;ch stabilize against
latera] or medial forces.
In contrast, the relatively flexible front-to-rear
stabilization systems provided by these braces permit relative
movement of the tibia and femur along the sagittal plane.
In addition, because rotary stability is a function of
both medial-lateral and anterior-posterior stability, the imple-
mentation of conventional knee brace designs tends to be less
effective than desired in any derotation function. Furthermore,
stabilization in all aspects is closely related to the effective
suspension of the orthotic device on the knee and leg in a manner
such that the device does not alter or shift its position on the
leg as by planing. Many prior art devices experience planing and
shifting which de-tract from their ability to provide medial-
lateral stabilityl anterior-pos-terior stability and/or rotatory
stability.
In addition to the difficulty of achieving adequate
suspension stability using typical prior art knee braces, fre~uen-
tly such braces avoid the problems associated with flexion by
restricting movement of the knee. Because of restrictions on
movement and because of weight, the use of these braces to preven-t
injuries puts the athlete at such a competitive disadvantage that
knee braces are not widely used for injury prevention. Rather,
the primary use has been remedial, to compensate for and protect
against existing injuries and weaknesses in already damaged and/or
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unstable knees. Perhaps the one exception to t'ne use of prior art
knee braces for remedial purposes rather than prevention is the
class of braces which cons;st simply of a pair of upright bands on
the sides of the leg. These are usecl to provide some means of
protection against medial-la-teral forces.
SUMMARY OF THE INVENTI~N
Accordingly, it is one object of the present invention
to provide a new and improved knee brace suspension system which
restricts planing and other movemen-t of the knee brace relative to
the leg and knee~
It i9 another object of the present invention to provide
a new and improved knee brace which protects against displacement
and injuries to the anterior cruciate ligament.
It is another object of the present invention to provide
a new and improved knee brace which protects against displacement
and medial-lateral, anterior-posterior and rotary instabilities.
In one embodiment, -the knee stabili~er of the present
invention contains a relatively rigid anterior tibial shell which
substantially conforms to the outline of the leg proximate and
~0 distal to the knee; a relatively rigid posterior femural shell
which substantially con-forms to the outline of the thigh proximate
the knee; and a pair of uprights extending one on the lateral side
of the knee and one on the mediaL side of the knee for rigidly
interconnecting the tibial and femural shells, and substantially
tracking flexion of the knee. The tibial shell wraps partially
around the posterior side of the leg, defining a posterior
opening, and the femural shell wraps partially around the anterior
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side of the thigh, defining an anterior opening, and has a pair of
suspension pads located on opposite sides of the patella between
the patella and the Eemural epicondyles. A strap-type clos~lre
means is attached at each of the anterior femural opening and the
posterior tibial opening for closing each opening to complete the
suspension of the stabilizer. The combination of the partially
open anterior tibial and posterior femural shells, the strap
closure means and the uprights provides a combination of light
weight, yet excel]ent anterior-posterior, medial-lateral and
rotary stability.
In a preferred working embodiment, the uprights are part
of a closed, rigid band support system including a femural section
which is attached to the uprights on opposite sides of the femural
shell and spans the posterior side of that shell, and a tibial
section which is attached to the uprights on opposi-te sides of the
tibial shell and spans the anterior side of that shell.
In a presently preferred, light-weight working version,
my knee stabilizer is configured as a four-point pressure system.
Here, the posterior border of the femural shell forms the first
pressure point, and the femural shell anterior strap means
supports an anterior plate for providing a second pressure point
at about the height of the superior border of the femural shell,
for cooperatively locking the femur to the Eemural shell and to
the band system. The posterior strap of the tibial shell again
forms the third pressure point. The tibial section of the band
system is positioned at the closed superior border of the
otherwise open anterior periphery of the tibial shell to form the
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fourth pressure point and, in cooperation with the third pressure
point, provldes a light-weight, two-poin-t pressure syste~ for
locking of the tibia to the tibial shelL and to the band system.
The tibial she]l preferably includes a circumferential superior
strap which completes the enclosure of the tibial shelL about the
leg, or itself spans the circumference of the leg for, tibial
inertial control, and for providing a stable suspension in
conjuction with the suspension pads. The four-poin-t pressure
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system provides medial-lateral, an~erior-posterior, and rotary
stability.
DETAILED DESCRIPTION
One preferred emhodimen~ 70 of the knee stabilizer of the present
invent1on is shown in FIGURES 7, 8 and 9. The knee stab:ilizer 70
comprises a tibial shell 71, a femural shell 72 and a ~losed b~nd
s~ructure 80 whi~h
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joins the two shells and inc]udes a jolnt 86 on either side of the
knee for substantially tracking flexion of the knee. The shells
and band are care-fully tailored and conEigured to conorm to the
shape and size of the individual leg and knee. The tibial shell
71 includes superior (upper) and inferior (lower) borders or
sections 96 and 97 which span the anterior (front) side thereof
and, particularly in applications re~uiring light weight, may be
open at the posterior (rear) side. The phrase "anterior tibial
shell" as used herein thus refers to -tibial shell 71 having one or
more sections which span the anterior side of the lower leg.
Similarly, the -femural shell 72 is closely configured to the size
and shape of the thigh, and has a support section 7~ which spans
the posterior side of the thigh. Thus, as used here, the phrase
"posterior femural shell" refers to a femural shell 72 which has a
section 74 spanning the posterior side of the thigh. In addition,
the tibial shell 71 has sections 75-75 which partially wrap around
the posterior of the leg and the femural shell 72 has sections
76-76 which wrap partially around the anterior section of the
femur. One purpose of these partial sections is to enhance the
suspension characteristics of the leg; at the same time, the open-
ings defined between sections 75-75 and between sections 76-76
contribute to the light weight and ease of application of the
stabilizer 70.
The anterior sections 76-76 of the femural shell each
include a stabilization or suspension tab 77 which is configured
to and positioned between the patella or knee cap and the femural
epicondyle located on that side of the knee. The tibial and
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- 11 - 61051-1965
femural shells have straps 78 and 79 respectivel~ attached thereto
for spanning their respective posterior and anterior openings to
aid the suspension of the shells on the leg and thigh.
Typically the straps 78 and 79 are rigidly attached
along one side, as by metal rivets, and are releasably attached on
the opposite side, as by Velcro, to permit releasing the straps to
fit the knee stabilizer onto the leg and to provide an adjustably
snug fit of the knee stabilizer 70 onto the leg.
Referring in particular to FIG. 7, the tibial and
femural shells 71 and 72 are rigidly suspended relative to one
another and the knee by the band suspension system 80. This
system comprises metal bands which are configured -to the outline
of the shells and leg. The system includes a pair o~ substan-
tially vertical uprights 82-82 attached to the medial and lateral
sides of the femural shell 72 and, similarly, a pair of substan-
tially vertical uprights 83-83 attached to the medial and lateral
sides of the tibial shell 71. A tibial band 84 is attached to the
uprights 83-83 on opposite sides of the tibial shell 71 and spans
the closed anterior section of the shell. Similarly, a femural
20 band 85 is attached to the uprights 82-82 on opposite sides of the
femural shell and spans the posterior side of the femural shell.
The uprights 82 and 83 are joined proximate the knee by a conven-
tional polycentric knee joint 86 which is designed to pivot in a
curve which tracks the knee, i~e., is similar to the anatomical
movement of the knee.
The knee stabilizer 70 includes severa] advantageous
suspension features. It should be noted that -the word "suspen-
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sion" refers to retaining a knee brace on the knee and leg without
movement, such as planing, of the brace relative to the knee.
Suspension, of course, con-tributes to the ability of the brace to
stabilize the knee and leg and many of the factors which are
necessary for adequa~e suspension also contribute to stabiliza-
tion. That is, improving suspension improves stabilization. One
advantageous feature of stabilizer 70 is the custom-tailored
contour of the shells 71 and 72 and band system 80. In being
precisely configured to the shape of the leg and thigh, both at
the anterior and posterior sides as well as the medial and lateral
sides, a secure fit is provided and movement of the stabilizer
relative to the leg is inhibited. A second, related aspec-t is
that the closely configured shells of the stabilizer 70 also en-
compass or cover more of the perimeter of the leg and thigh than
conventional braces. Third, the rigid band support system 80
comprises a unitary configuration which tracks the primary stress
points (the back of the thigh, the front of the tibia, and the
sides of the legs), and thereby keeps the configured shells firmly
in place on the leg and contributes to excel]ent stability. Also,
as mentioned above, the polycentric knee joints 86-86 track in a
curve much the same as does the knee, which facilitates maintain-
ing the shells in position during flexion and extension of the
knee. Fifth, the knee joint 86 can be misaligned slightly. That
is, (l) the joints can be rotated slightly relative to the anato-
mical track to create a stabilizing force at the anterior superior
edges of the tibia to stabilize rotatory instabilities or (2) the
knee joint 86 can be misa]igned or offset relative to the anatomi-
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cal knee so that the plastic material of the shell bends faster
than the knee and thus maintains presgure on the knee to counter
anterior cruciate instabillty of the knee. E~or example, the joint
86 can be posi-tioned posteriorly and/or superiorly relative to the
anatomical knee center to counter the inherent instability of the
knee during 20-60 of flexion, or the joint can be positioned
rotationally to the knee center to counter the an-terior rotatory
displacements of the tibia. An example of such positioning is
illustrated in FIG. 7 wherein the orthosis knee center provided at
knee joint 86 is positioned above the anatomical knee center 87
so that, e.g., in flexing as shown in phantom by line 880 the
orthosis flexes faster than does the knee at 88A and creates
posterior pressure on the knee and leg.
Sixth, the brace incorporates a circumferential peri-
meter differential. That is, the distal border (lower portion) of
the femural shell 72 has a smaller circumference than the adjacent
underlying femural condyles. This is done to apply pressure to
the anterior edges of the abductor and adductor epicondyles on the
medial and lateral sides of the femural condyles. A seventh,
related feature is the suspension tabs 77-77 which are discussed
below. Finally, but not to exhaust the advantages, an auxiliary
strap can be usea to connect the superior border of the tibial
shell to provide additional stabilization again~t inertia in
unusually high stress situations.
In considering the stabilization characteristics of -the
knee stabilizer 70, refer initially to the front and rear depic-
tions of FIGS. 8 and 9, as well as the side view of FIG. 7. In
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contrast to prior art braces, the stabilizer 70 stabilizes ayainst
medial-lateral forces very well, in part because the sheLls 71 and
72 circumferentially encompass ~lore of the leg than prior art
braces. The shells fully cover both the lateral and medial sides
of the thigh and leg proximate the knee. Displacement side-to-
side is further constrained by the closed anterior section of the
tibial shell 71, the partial wraparound of the posterior section
75 of the tibial shell, the closed posterior section of the
femural shell 72 and the partial wraparound of the anterior
section 76 of the femural shell, in conjunc-tion with the addi-
tional constraint agains-t side-to-side displacement provided by
the closed configuration of band 80, that is the posterior femural
band 85, the anterior tibial band 84 and the interconnecting up-
rights 82 and 83. In contrast to the three-point medial-lateral
suspension of many prior art braces, the described construction of
the knee stabilizer 70 provides essentially continuous support and
stabilization against displacement from the lower or distal edge
of the tibial shell 71 to the upper or superior edge of the
~emural shell 72.
Those skilled in the art will appreciate that the above-
described structural features which provide medial-lateral stabil-
ity also contribute to anterior-posterior stability. The struc-
ture of the knee stabilizer 70 incorporates key pressure points
which are designed to protect against anterior-posterior instabil-
ity as well as medial-lateral and ro-tary instability. ReEerring
to FIG. 7, five of these points are indicated generally by the
arrows designated 91-95. These include three pressure points or
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regions which securely lock tlne tibia: the distal ~lower) 9l and
proximal (upper) 92 borders of the closed anterior tibial shell
section 73, and the posterior point 93 defined by the posterior
section and elastic strap 78 of the tibial shell; and two fernural
pressure points: the anterior proximal (superior) femural border
94 and the posterior distal border 95 of the closed posterior
section 74 of the femural s~lell. Also, due to the large amount of
tendon motion in the distal posterior border of the -femular
section, the inverted popiteal-shaped relief 74 is preferably set
in a slight lateral tilt.
Those skilled in the art will quickly appreciate that
the other structural features such as tabs 77-77 also serve
important stabilization functions.
The effectiveness of this suspension and pressure system
design can be illustrated by considering application of the
anterior tibial force 21 shown in FIG. 2A and the external rota-
tion anterior tibial force 21-22 shown in FIG. 2B. As indicated
previously, these are frequently responsible for injury to the
anterior cruciate ligament, perhaps the most frequency injury in
sports. In response to an anterior tibial force 21 of sufficient
magnitude, the tendency is for the lower leg 12 to move and poten-
tially injure the anterior cruciate ligamen-t. However, this move-
ment transmits pressure against the closed borders 96 and 97 of
the anterior section 73 of the tibial shell 71 and tends to move
the tibial shell. This tendency is in turn transmitted via the
band support system 80 and femur band 85 thereof to the femural
shell 72. The closed posterior section 74 and, in particular, the
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distal border pressure 95 transmit a~y displaceMent of the lower
leg into like displacement of the thlgh and thereby prevent dis-
placement of the tibia 12 relative to the femur 11. In short, the
anterior-directed tibial force 21 is transmitted as an anterior-
directed femural force to stabilize the femur and tibia and
prevent relative displacement.
Considering now the rotational component 22 of the
exterior force, one will recall that the tendency of prior art
braces is to rotate on the ley. In the knee stabilizer 70, an
additional stabilizing influence to those previously described is
provided by the stabilizing pads 77-77 which provide pressure at
the distal border oE the anterior femural shell section 76. In
response to such rota-tional forces (either or both anterior-
lateral or anterior-medial), one of the pads 77 is constrained
from movement by the opposite epicondyle, while the other pad is
constrained by the patella. As a result, the anterior cruciate
ligamen-t is stabilized, along with the other knee ligaments and
the entire knee. In addition, those skilled in the art will
appreciate that rotational forces and rotary instability are
functions of the force vectors in the frontal plane (medial-
lateral forces) and the sagittal plane (anterior-posterior
forces). Thus, derotation and ro-tary stability are aided by the
features described previously which contribute to enhanced
anterior-posterior stability and medial-lateral stability.
In working embodiments of the knee stabilizer 70
designed for a six foot, 180 pound male, the overall length oE the
stabilizer was 19.5 inches. The femural shell was polypropylene
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plastic three-sixteenths of an inch thick while the tibial shell
was one-eighth inch thick polypropy:Lene. The shells were lined
with one-~uarter inch thick medium densit~ aliplast. The bands
and uprights were both made of 2024 alurninum al]oy to provide
light weight and strength. The bands ranged from one-eighth by
three-quarters inch to one-eighth by one and one-haLf inch,
depending upon -the patient's size and activities, while the
uprights were one-eighth by three-quarters of an inch. The joints
were Becker 1009B aluminum polycentric knee joints, formed by
machining to provide enhanced smoothness and tracking. Silver
solder can be inserted into the joint gear to limit flexion to a
prescribed range. The straps 78 and 79 were gum rubber reinforced
by leather at the Velcro* and Dacron* at the copper rive~ attach-
ment points. The resulting stabilizer weighed 24-40 ounces and
provided excellent movement and mobility.
A presently preferred, four-point pressure version 70'
is illustrated in FIGS. 10-12. Specifically, the stabilizer or
brace 70' is a three-point pressure system with a fourth inertial
control strap. In describing the four-pressure point brace 70',
components which correspond to, or are modified versions of,
components of the five-pressure point brace 70 illustrated in
FIGS. 7-9 are identified by corresponding numbers differentia-ted
by the prime symbol. Thus, for example, the modified tibial shell
71' of the four-point pressure brace 70' corresponds to the tibial
shell 71 of the five-poin-t pressure brace 70.
The femural shell 72' of the four-pressure-point brace
70' includes elongated medial and lateral sections 76'-76' which
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extend farther up the thigh than do the corresponding components
76-76 of brace 70, FIG. 7. Anterior strap 79 is omitted. In ;ts
place is provided a typica]ly elongated anterior plate 98 which is
positioned between the e:Longated medial and lateral upriyht
section 76'-76'. The anterior plate 98 typically is moun-ted to
the femural shell 72' by a pair of straps or belts 99-99. The
belts 99-99 can be single-piece con-tinuous straps which are
fastened by buckles, Velcro, etc.
In the illustrated embodiment, each belt 99 includes a
strap or belt section 101 which is riveted at one end to one up-
right section 76' of the femural shell and mounts a buckle 102 at
the loose end. A second strap or belt section 103 is attached by
rivets to the other upright section 76' of the femural shell 72'.
The belt section 103 also extends across, and is riveted to, the
plate 98, and is of sufficient length to permit looping of its end
104 through the buckle 102 to provide an adjustable, loop-back
fastening or closing of the belt 99.
Typically, each belt 99 is adjustably fastened by, for
example, mating lengths of Velcro fastening material 105 which are
attached to the outer-facing surface of the inner portion of the
belt section 103 and to the inner-facing surface of the overlap-
ping end 104 of the belt section 103. The belts 99 can be elastic
material but, preferably, are formed of inelastic material such
as Dacron. An inelastic or fixed system provides better anterior
pressure on the quadricep muscle and also transfers force better
than an elastic system. As a result, the femural pressure poin-t
at 94' is improved. The other, second femural pressure point is
provided by the posterior border 74' of the femural shell 72'
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and the associa-ted posterior femural band 85' corresponding to the
pressure point 74 of the five-pressure-point shell 70. ~uite
obviously, an inelastic, fixed belt or strap syste~n can be
implemented in the five-pressure-point system 70 as well as in the
present four-pressure-point system 70'.
Referring further to FIGS. 10-12, the tibial shell 71'
of the four-pressure-point brace is shorter, smaller and therefore
of lighter weight than the tibial shell 71, FIGS. 7-9. The tibial
shell 71' provides two pressure points (the third and fourth
system pressure points), rather than the three points of the
alternative five-pressure-point embodiment 70. The narrower
elastic band or strap 78' which spans the posterior opening of the
tibial shell 71' provides the third pressure point of the system.
The fourth pressure point of the brace is provided at the superior
anterior band 96' of the tibial shell 71'. To decrease weight,
the lower anterior band 97 of the five-pressure-point brace 70
(FIG. 7) is omitted and, as a consequence, the lower ends of the
medial and lateral upright shell sections 73'-73' terminate in the
open configuration which is shown most clearly in FIGS. 8 and 9.
In addition, the anterior tibial band 84' of the band pressure
system is moved to the superior band or border 96' to enhance the
rigidity and support at the fourth pressure point. Suspension of
the tibial shell 71' on the leg is further enhanced by a circum-
ferential strap or belt 106 which spans the circumference of the
leg. While various constructions and means of attaching the belt
106 are possible and in fact, while it need not be attached to the
tibial shell 71', the belt 106 typically is attached to the tibial
~r
-- 20 - 6105~ 1965
shell 71' by rivets and is closed by using lengths of Velcro 107
which are attached to the outer-facing surface of the belt and to
the inner-facing surface of the overlapping end of the belt.
In summary, in the four-pressure--point brace 70', the
lower anterior band 97 of the tibial shell is eliminated and the
metal strut 84 of the band system is moved vertically, as shown at
84', and incorporated into the upper anterior tibial band 96' n
The posterior elastic band 78' of the tibial shell is more narrow
than band 78. Also, the anterior elastic band 7g of the femural
shell has been replaced by an ine]astic Eixed-strap system which
incorporates belt(s) 99 and anterior pressure plate 98.
Referring specifically to FIG. 10, in addition to
lighter weight, this alternative brace construction 70' provides
an improved pressure system. As mentioned, the four-point
pressure system is effectively a three-point pressure system with
a fourth, inertial control strap, the posterior tibial strap 78'.
The Eour pressure points are first, the posterior femural point
95'; second, the anterior femural point 94'; third, the above-
mentioned posterior tibial point 93'; and fourth, the anterior
tibial point 92'. The objective of the system is to apply Eorce
at anterior tibial point 96', using the brace and its band system
as a lever system and the posterior femural point 95' as the
fulcrum. Pressure is applied at the anterior femural point 94' by
the adjustable strap system 99. That is, when pressure is
increased at pGint 94' by tigh-tening the belts 99, the femural
section of the band system is pulled anteriorly. ~his force is
transmitted through the fulcrum a-t 95' and therefore pivots the
1~
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- 21 - 61051-1965
tibial section of the band system, along wlth the knee joints and
the band section 96', posteriorly. ~s a result, tightening at one
point, using belts 99 securely suspends the knee stabilizer 70' on
the leg and provides an optimum combination of light weight an~
anterior-posterior, medial-lateral and rotary stability.
In a working embodiment of the knee stabilizer 70',
designed for a six foot, 180 pound male, the overall length of
the stabilizer was 19.5 inches. Both the femural shell and the
tlbial shell were one-eighth inch thick polypropylene plastic.
The shells were lined with one-eighth inch thick medium density
aliplast. The bands and uprights were both made of 2024 aluminum
alloy to provide light weight and strength. The bands measured
one-eighth inch by three-quar-ters of an inch, while the uprights
were one-half inch by one-eighth inch. The pivotal joints of the
band system were Becker lOO9C aluminum polycentric knee joints,
formed by machining to provide enhanced smoothness and tracking.
The posterior tibial strap was gum rubber reinforced by leather at
the Velcro and by Dacron at the Speedy rivet attachment points.
The anterior femural pressure plate was also formed of one-eighth
inch thick polypropylene and the Vacron attachment straps were
riveted to the plate and to the femural shell by Speedy rive-ts.
The resulting knee stabilizer weighed between 14 and 24 ounces,
depending upon the size and girth of the patient and the patient's
activities, and provided excellent movement, mobility and stabil-
ity.
The combination of light weight, freedom of movement and
stabilization provided by the above-described four-pressure-point
.~
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'. ' ` ' ' ' "' ":': "' '
,.
- 2:L~ - 61051-19~5
and five-pressure-point embodiments of the knee stabilizer or
brace 70 make it suitable for both preventive and remedial use.
For light weight and preventive use, the thickness oE the
materials can be reduced, the shells can be drilled or extensive
use made of apertures or other openings and the size of the solid
anterior and posterior sections reduced. To give only one illu5-
tration of the value of such preventive use, in the National Foo-t-
ball League, approximately 50 percent of injuries involve -the
knee. This means during the 1983 season perhaps five to seven of
the fourteen linemen on each team will have suffered disabling
knee injuries. This figure could be substantially reduced by the
preventive use of an effective knee stabili~er.
For remedial use to protect against further aggravation
of existing ~njuries and instabilities, the thickness and other
dimensions can be tailored as required by the orthotics special-
ists to fit individual needs. In addition, in applications
requiring very great strength and stability, albeit at the sacri-
fice of slightly greater weight, a material such as stainless
steel can be used for the band system. One potential use which
might require -this substitution is mountain climbing, where safety
considerations are paramount and repair or replacement may not be
available.
Having thus described the knee stabilizer which embodies
the principles of my invention, and specific examples of its use,
the invention which I claim is:
